DESCRIPTION (provided by investigator): This application is in response to NIAID's request for high-priority biodefense products specific to CDC Category A-C Priority Pathogens. It focuses on the development of compounds with selective activity against Bacillus anthracis, included in the highest priority group, Category A. The goal of this application is to show proof-of-principal for potential antimicrobial targets in a specific biosynthetic pathway of Bacillus anthracis that will allow for the development of compounds that can be used to treat anthrax. At least two enzymes in this pathway represent targets that are naturally resistant to standard antimicrobial agents. As a result, traditional drugs for these targets are currently not recommended for treatment of anthrax. We hypothesize that these targets are amenable to new drug development and that they may be susceptible to non-traditional antimicrobials that may already exist in chemical repositories. Consequently, one goal of this project will be to implement the most expedient way to screen drugs that are already available against these enzyme targets. Because the degree of homology of these enzymes is so high, we hypothesize that B. cereus can be used in place of Bacillus anthracis. This will facilitate the use of high-throughput screening with a robotics system in a BSL-2 versus a BSL-3 facility. The approach will be to use DNA recombinant technology coupled with X-ray crystallographic molecular modeling to demonstrate proof-of-principal with regard to functional similarities of two key enzymes in an essential metabolic pathway of Bacillus anthracis. Recombinant enzymes will be used in drug-screening assays and for crystallization to develop effective three-dimensional models to confirm enzyme similarities. If successful, this strategy would prove useful for other enzymes in this pathway that also share a high degree of homology. This R21 application is intended to lay the groundwork for a subsequent RO1 that will be designed to attain narrow-spectrum antibiotics for Bacillus anthracis through early product development resulting from collaborations between academic researchers and industrial laboratories.